Yes. This is one of the most misunderstood areas of personal injury law, and the misunderstanding almost always runs in the same direction: people who were injured in accidents assume that because they already had a bad back, a prior knee surgery, a history of migraines, or some other pre-existing condition, they have a diminished claim or perhaps no claim at all. Insurance adjusters encourage this assumption. They will point to your medical history and suggest that what you are experiencing now is simply a continuation of what you had before, that the accident did not really cause your current pain, and that their client cannot be held responsible for a condition that predates the crash. That argument sounds logical until you understand the actual legal standard that governs these situations, at which point it falls apart almost entirely.

The legal doctrine that controls pre-existing injury cases is called the eggshell plaintiff rule, and it is one of the oldest and most settled principles in American tort law. The rule holds that a defendant takes a plaintiff as they find them. If you were more vulnerable to injury than the average person because of a prior condition, that is not a defense to liability. The at-fault driver does not get credit for the fact that a healthier person might have walked away from the same crash with nothing more than a sore neck for a few days. If your vulnerability caused your injuries to be worse than they would have been for someone without your history, the at-fault driver is responsible for the full extent of the harm they caused — including the portion that is attributable to the interaction between the impact and your pre-existing condition. This principle applies in Missouri and in every other state. It is not a plaintiff-friendly innovation of recent decades. Courts have applied it for well over a century because it reflects something straightforward: you do not get to choose who you injure, and the frailty of the person you hurt does not reduce your responsibility for hurting them.

The more precise framework your case will actually be analyzed under is the aggravation of a pre-existing condition doctrine. The distinction between a brand new injury and an aggravated pre-existing condition matters for how your damages are calculated, but it does not change whether you have a valid claim. What you are entitled to recover is the difference between where you were before the accident and where you are now — the additional pain, the additional functional limitations, the additional medical care, the additional lost wages that would not exist but for the crash. If your back was already causing you some level of daily discomfort, and the accident turned that manageable discomfort into a condition requiring surgery, you can recover for the surgery, the recovery, the future care needs, and the pain and suffering associated with the worsened condition. You are not trying to recover for the pre-existing condition itself. You are recovering for what the accident did to it.

Here is where the distinguishing insight lives, and it is one that changes how people approach these cases in a concrete way: the insurance company’s strategy in pre-existing condition cases is not to deny that the accident happened or even that you were hurt. Their strategy is to blur the line between what existed before and what the accident caused, and to use that blurriness to minimize what they owe. They will obtain your prior medical records — all of them, sometimes going back a decade or more — and they will look for every complaint, every diagnosis, every imaging study that mentions the area of your body that is now at issue. Then they will present that history as evidence that your current condition is simply the natural progression of what you already had, that you would be in the same place regardless of the crash. The antidote to that strategy is not to hide your prior history or downplay it. The antidote is a treating physician who can clearly articulate, in their medical records and in a report or deposition if necessary, what your baseline was before the accident, what changed as a result of the accident, and why those changes are causally connected to the crash rather than to the pre-existing condition’s natural progression. That medical opinion is the spine of your case, and it needs to be built carefully from the beginning.

The practical implication of this is that honesty with your doctors and your attorney about your prior medical history is not just ethically required — it is strategically essential. People sometimes try to minimize or omit prior injuries when they are describing their symptoms to treating physicians after an accident, because they are worried that the history will undermine their claim. This instinct is understandable and it is almost always counterproductive. Insurance companies will obtain your prior records regardless of what you say to your doctors. If those records show a history of back pain and your post-accident records make no mention of it, the defense will argue that you were concealing relevant information, which damages your credibility on everything else. If your treating physician did not know about your prior condition and therefore did not account for it in their causation analysis, their opinion becomes vulnerable to attack. A doctor who knows your complete history and can still point clearly to what changed after the accident is a far more powerful witness than one who was operating without relevant information and whose analysis can be undermined by records they never saw.

Your prior medical records are also likely to become a significant battleground in discovery if your case goes into litigation. In Missouri and most other jurisdictions, defendants in personal injury cases are entitled to obtain medical records relevant to the claims and injuries at issue. When a pre-existing condition is involved, courts have generally allowed broad discovery into prior treatment for the affected body part, because that history is genuinely relevant to the causation question. What this means practically is that records you may have forgotten about — treatment from years ago, imaging studies from a prior incident, notes from a primary care physician who mentioned your complaint in passing — can surface and become part of the case. Your attorney needs to know about these things before the defense finds them, not after, because context and framing matter. A prior MRI showing disc degeneration at L4-L5 is very different evidence when your attorney has already built a narrative around your pre-existing condition than when it appears for the first time in a defense filing designed to surprise.

The gap between your pre-accident baseline and your post-accident condition is something that needs to be established with actual evidence, not just your testimony about how you feel now versus how you felt before. Objective evidence of the baseline is particularly valuable. Prior imaging studies are actually useful here, even when they show pathology, because they give you a documented picture of what existed before the crash. If a pre-accident MRI shows mild disc bulging with no nerve involvement, and a post-accident MRI shows a herniation at the same level with significant nerve compression, that comparison is powerful evidence of what the crash did to a condition that had previously been manageable. Conversely, if the only evidence of your pre-accident baseline is your own recollection that you felt fine, the defense has more room to argue that your current condition is simply what the pre-existing problem looked like as it continued to develop. Documentation of function is often as important as documentation of pathology. Records showing you were working full time, exercising regularly, participating in activities that your current condition now prevents, establish the lived reality of your baseline in a way that resonates with adjusters, mediators, and juries.

Witness testimony about your pre-accident condition and functioning can fill gaps that medical records cannot always capture. People who knew you before the accident — coworkers, family members, friends — can speak to what you were able to do physically, how you moved, whether you appeared to be in pain, what activities you participated in. This kind of testimony is not a substitute for medical evidence, but it provides a human dimension to the baseline question that objective records sometimes lack. A neighbor who saw you playing with your children in the yard every weekend before the accident, and who has watched you struggle to get out of a car since, is telling the jury something that no MRI report conveys. Your attorney should be thinking about this category of evidence from early in the case, not as an afterthought during trial preparation.

There is a specific type of pre-existing condition that creates particular complications, and it is worth addressing directly: prior injuries to the same body part from a prior accident, particularly one in which you received a settlement or made a claim. If you settled a prior back injury claim three years ago and now you are claiming a back injury from a new accident, the defense will attempt to use the prior settlement as evidence that your current condition was already compensated, that the prior accident rather than this one is the source of your problems, or that you are a frequent claimant whose credibility deserves skepticism. None of these arguments are legally sound if the current accident genuinely caused a new injury or worsened a condition that had stabilized after the prior incident, but they create a more complex factual landscape that requires careful medical and legal development. Your treating physician needs to be able to distinguish what you presented with after the prior injury, what your baseline was after that recovery, and what this new accident added on top of it. Without that clear medical narrative, the prior claim becomes a significant complication rather than simply a piece of background context.

The psychological dimension of pre-existing conditions is also something that gets underweighted in these cases. If you had a history of depression or anxiety before the accident, and the accident significantly worsened your mental health — through chronic pain, loss of function, financial stress, or the trauma of the crash itself — that aggravation of a pre-existing psychological condition is compensable on the same terms as a physical one. The eggshell plaintiff rule does not have a carve-out for mental health. Insurance companies are often more resistant to psychological injury claims than physical ones, and they are particularly resistant when there is a prior history, but resistance is not the same as a valid legal defense. Documentation through consistent mental health treatment, a clear causation opinion from a treating therapist or psychiatrist, and evidence of functional impact are the same building blocks that support a physical injury claim, applied to a different category of harm.

The clearest way to think about all of this is that a pre-existing condition is not a barrier to recovery. It is a complication that requires more careful medical documentation, more strategic case development, and a more deliberate approach to establishing causation. The insurance company wants you to believe your history makes your claim weak. In the hands of an attorney who understands how to develop these cases, your history is something that can be contextualized, explained, and distinguished in ways that make clear exactly what the accident cost you — not what you were already carrying. Those are different things, and the law has always recognized the difference.

This content is intended for general informational purposes only and does not constitute legal advice. The law governing pre-existing conditions and personal injury claims varies by jurisdiction and depends heavily on the specific facts of each case. Nothing here should be relied upon as legal advice for your situation. Consult a licensed personal injury attorney before making any decisions about your claim.